• Proceedings of the KSME Conference
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• 2001.11b
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• pp.493-498
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• 2001

In the low velocity displacement air-conditioning system, the conditioned air is supplied from the diffuser placed on the wall near the floor and vented near the ceiling. This system has some advantages upon the traditional mixing system; the air quality near the people is improved by the displacing action of the system and the energy may be saved by neglecting the cooling or heating load for the upper space of the space above the people. This study is to examine the temperature and velocity distributions in the room and near the diffuser. It is found that the temperature is stratified uniformly all over the room space to show the displacing function of the system.

• Interaction and multiscale mechanics
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• v.2 no.4
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• pp.413-430
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• 2009

The stator tooth is a key component of the electromechanical integrated toroidal drive system. The stator tooth is spiral in shape and the calculation of its displacements is difficult. In this paper, using the coordinate transformation method, the displacements of the stator tooth in the local coordinate system are expressed as the function of the variable in the drive coordinate system. Using the minimum potential energy principle, the equations of the displacements of the stator tooth under the loads are deduced. The displacement distributions within the stator tooth are investigated and the changes of the displacement distributions along with the main parameters are analyzed. This research can offer the basis for the strength and stiffness design of the drive system.

• Structural Engineering and Mechanics
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• v.29 no.6
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• pp.643-658
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• 2008

In this paper, we present a quadratic element model based on non-conforming displacement modes and modified shape functions. This new and refined 8-node hybrid stress plane element consists of two additional non-conforming modes that are added to the translational degree of freedom to improve the behavior of a membrane component. Further, the modification of the shape functions through quadratic polynomials in x-y coordinates enables retaining reasonable accuracy even when the element becomes considerably distorted. To establish its accuracy and efficiency, the element is compared with existing elements and - over a wide range of mesh distortions - it is demonstrated to be exceptionally accurate in predicting displacements and stresses.

• Proceedings of the KSME Conference
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• 2000.04b
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• pp.132-137
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• 2000

A complete theoretical treatment of the photothermal displacement technique has been performed for thermal diffusivity measurement in solid materials. The influence of parameters - radius and modulation frequency of pump beam and thickness of material - on the phase lag was studied. The phase decreases up to a certain position, then starts to increase and does have an asymptotic value. The position, where phase has the minimum value, is a function of thermal diffusion length thickness of sample, and radius of pump beam. A new method based on minimum phase lag is described to determine the thermal diffusivity of solid material.

• Journal of the Korean Society for Precision Engineering
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• v.19 no.9
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• pp.179-185
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• 2002

Solid state deformation of PZT is effective for the micron scale displacement. Inch-worm gets large linear displacement by incrementally summing displacements of PZT actuators. Dynamic stiffness of inch-worm is generally low compared to its driving condition due to the small size and light weight of inch-worm. Mechanical vibration induced by low stiffness may degenerate the motion accuracy of the inch-worm. In this paper, dynamic characteristics of the inch-worm are modeled by using the frequency domain curve fitting based on the experimental frequency response function. SMC (sliding mode control) is examined for motion control of the inch-worm. Simulation and experimental results show that the inch-worm with SMC scheme is feasible for the precise displacement device.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.15 no.2 s.95
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• pp.123-128
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• 2005

Forced vibration of a thin circular ring with a concentrated harmonic force is analyzed when the ring is free and has only the in-plane motion. Using the unit doublet function for external force, the governing equation is obtained and is solved by the use of Laplace transform. The exact solutions of displacement components and bending moment are obtained. In order to verify the solutions of analysis, finite element analysis is performed and the results shows good agreement. Then, frequency response curves for displacement and bending moment are obtained. In deriving the governing equations and the solutions, nondimensional parameter of the exciting frequency and the magnitude of exciting force are extracted. As the displacement components are obtained, the remaining bending strain, slope, curvature, shear force, etc. can also be derived. With the results of this work, the responses of a free ring excited on multiple points with different frequencies can also be obtained easily by superposition.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2000.10a
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• pp.369-376
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• 2000

For the general loading condition and boundary condition, it is very difficult to obtain closed-form solutions for buckling loads and natural frequencies of thin-walled structures because its behaviour is very complex due to the coupling effect of bending and torsional behaviour. Consequently most of previous finite element formulations introduced approximate displacement fields using shape functions as Hermitian polynomials, isoparametric interpoation function, and so on. The purpose of this study is to calculate the exact displacement field of a thin-walled straight beam element with the non-symmetric cross section and present a consistent derivation of the exact dynamic stiffness matrix. An exact dynamic element stiffness matrix is established from Vlasov's coupled differential equations for a uniform beam element of non-symmetric thin-walled cross section. This numerical technique is accomplished via a generalized linear eigenvalue problem by introducing 14 displacement parameters and a system of linear algebraic equations with complex matrices. The natural frequencies are evaluated for the non-symmetric thin-walled straight beam structure, and the results are compared with available solutions in order to verify validity and accuracy of the proposed procedures.

• Proceedings of the KIEE Conference
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• 1993.07b
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• pp.993-996
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• 1993

This paper presents the static thrust of a hybid-type LPM by coenergy method. First, the nonlinealities of the permanent magnet, the primary core and the secondary are interpolated by the cubic spline method. Then the equivalent magnetic circuit including airgap reluctance, which is a function of displacement, modelled by the permeance method is obtained. From the derivative of coenergy with displacement computed by Newton Raphson method, the static thrust is calculated at each displacement with certain exciting current.

• Structural Engineering and Mechanics
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• v.5 no.2
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• pp.177-191
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• 1997

In the paper, a fractional derivative Kelvin-Voigt model describing the dynamic behavior of a special class of fluid viscous dampers, is presented. First of all, in order to verify their mechanical properties, two devices were tested the former behaving as a pure damper (PD device), whereas the latter as an elastic-damping device (ED device). For both, quasi-static and dynamic tests were carried out under imposed displacement control. Secondarily, in order to describe their cyclical behavior, a model composed by an elastic and a damping element connected in parallel was defined. The elastic force was assumed as a linear function of the displacement whereas the damping one was expressed by a fractional derivative of the displacement. By setting an appropriate numerical algorithm, the model parameters (fractional derivative order, damping coefficient and elastic stiffness) were identified by experimental results. The estimated values allowed to outline the main parameter properties on which depend both the elastic as well as the damping behavior of the considered devices.

• Structural Engineering and Mechanics
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• v.69 no.5
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• pp.479-486
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• 2019

Based on the displacement general solution of a pre-twisted Euler-Bernoulli beam, the shape function and stiffness matrix are deduced, and a new finite element model is proposed. Comparison analyses are made between the new proposed numerical model based on displacement general solution and the ANSYS solution by Beam188 element based on infinite approach. The results show that developed numerical model is available for the pre-twisted Euler-Bernoulli beam, and that also provide an accuracy finite element model for the numerical analysis. The effects of pre-twisted angle and flexural stiffness ratio on the mechanical property are also investigated.